use sha2::{Digest, Sha256};
use std::path::{Path, PathBuf};

/// A builder of temp directory for tests purpose.
#[derive(Clone)]
pub struct TempDir {
    module_name: String,
    name: String,
    enable_short_path: bool,
    short_path_max_len: usize,
}

const TEMP_DIR_ROOT_NAME: &str = "mithril_test";
// 90 to have some room for the folder content (in case of restrained length like socket path)
const DEFAULT_SHORT_PATH_MAX_LEN: usize = 90;

impl TempDir {
    /// `TempDir` builder factory
    pub fn new<T: Into<String>>(module: T, name: T) -> Self {
        Self {
            module_name: module.into(),
            name: name.into(),
            enable_short_path: false,
            short_path_max_len: DEFAULT_SHORT_PATH_MAX_LEN,
        }
    }

    /// Change path generation in order to guarantee a path that have at maximum 90 characters.
    ///
    /// Typically used for cases when the generated folder will include a socket.
    pub fn generate_shorter_path(mut self) -> Self {
        self.enable_short_path = true;
        self
    }

    /// Set the max len that a short path can have
    pub fn set_short_path_max_len(mut self, max_len: usize) -> Self {
        self.short_path_max_len = max_len;
        self
    }

    /// Generate the path of the temp directory (no IO operation will be executed)
    pub fn build_path(&self) -> PathBuf {
        const SHA_LENGTH: usize = 10;
        let base_dir = std::env::temp_dir().join(TEMP_DIR_ROOT_NAME);

        // Short path only:
        // Combined max len should be lower than `self.short_path_max_len` to have some room for
        // the folder content.
        // MacOS temp folders are not in the `/tmp` folder but in a dynamic path adding 45 chars.
        // ie: /var/folders/_k/7j0m5c_n4g94vgx9gxknp4tm0000gn/T/
        if self.enable_short_path {
            // In order to discriminate two tests with the same name but within different modules
            // we append the short sha of the module+name to the path.
            let mut hasher = Sha256::new();
            hasher.update(&self.module_name);
            hasher.update(&self.name);
            let sha = hex::encode(hasher.finalize());
            let short_sha = &sha[0..SHA_LENGTH];

            // `-2` since when joining a path this adds a `/` and we also add a `_` to join the sha
            let max_path_len =
                self.short_path_max_len - SHA_LENGTH - 2 - base_dir.to_string_lossy().len();

            let max_len = self.name.len().min(max_path_len);

            base_dir.join([&self.name[0..max_len], "_", short_sha].concat())
        } else {
            base_dir.join(&self.module_name).join(&self.name)
        }
    }

    /// Create a directory based on the builder configuration in the system temp folder.
    pub fn build(&self) -> PathBuf {
        let path = self.build_path();
        self.create_dir(&path);

        path
    }

    /// Create on disk a temp directory based on the given module & name.
    ///
    /// Equivalent to:
    /// ```
    /// # use crate::mithril_common::test_utils::TempDir;
    /// TempDir::new("module", "name").build();
    /// ```
    pub fn create<T: Into<String>>(module: T, name: T) -> PathBuf {
        Self::new(module, name).build()
    }

    /// Create on disk a temp directory based on the given module & name, the generated path
    /// is guaranteed to be at most 90 characters long.
    ///
    /// Equivalent to:
    /// ```
    /// # use crate::mithril_common::test_utils::TempDir;
    /// TempDir::new("module", "name").generate_shorter_path().build();
    /// ```
    pub fn create_with_short_path<T: Into<String>>(module: T, name: T) -> PathBuf {
        Self::new(module, name).generate_shorter_path().build()
    }

    fn create_dir(&self, path: &Path) {
        if path.exists() {
            std::fs::remove_dir_all(path)
                .unwrap_or_else(|e| panic!("Could not remove dir {path:?}: {e}"));
        }

        std::fs::create_dir_all(path)
            .unwrap_or_else(|e| panic!("Could not create dir {path:?}: {e}"));
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::{fs, io::Write, ops::Not};

    #[test]
    fn non_short_path_are_in_a_mithril_test_slash_module_folder_structure() {
        let path = TempDir::new("temp_dir", "basic").build();

        assert_eq!(
            Some(
                std::env::temp_dir()
                    .join(TEMP_DIR_ROOT_NAME)
                    .join("temp_dir")
                    .as_path()
            ),
            path.parent()
        );
        assert!(path.exists());
    }

    #[test]
    fn short_path_are_in_a_mithril_test_folder_structure() {
        let path = TempDir::new("temp_dir", "basic_short_path")
            .generate_shorter_path()
            .build();

        assert_eq!(
            Some(std::env::temp_dir().join(TEMP_DIR_ROOT_NAME).as_path()),
            path.parent()
        );
        assert!(path.exists());
    }

    #[test]
    fn shorter_path_have_a_length_lower_than_90_chars_even_when_given_module_longer_than_that() {
        let path = TempDir::new(
            "module_longer_than_a_string_of_90_characters_so_this_test_can_fail_if_the_builder_is_a_bad_builder_that_do_nothing",
            "name",
        )
            .generate_shorter_path()
            .set_short_path_max_len(90)
            .build_path();
        let path_len = path.to_string_lossy().len();

        assert!(
            path_len <= 90,
            "path with `short` option enabled was longer than 90 characters:\n\
            path_len: `{path_len}`\n\
            path: `{}`",
            path.display()
        );
    }

    #[test]
    fn shorter_path_have_a_length_lower_than_90_chars_even_when_given_name_longer_than_that() {
        let path = TempDir::new(
            "mod",
            "name_longer_than_a_string_of_90_characters_so_this_test_can_fail_if_the_builder_is_a_bad_builder_that_do_nothing",
        )
            .generate_shorter_path()
            .set_short_path_max_len(90)
            .build_path();
        let path_len = path.to_string_lossy().len();

        assert!(
            path_len <= 90,
            "path with `short` option enabled was longer than 90 characters:\n\
            path_len: `{path_len}`\n\
            path: `{}`",
            path.display()
        );
    }

    #[test]
    fn same_name_but_two_different_module_generate_different_path() {
        let path1 = TempDir::new("module_a", "test").build_path();
        let path2 = TempDir::new("module_b", "test").build_path();

        assert_ne!(path1, path2);
    }

    #[test]
    fn same_name_but_two_different_module_generate_different_path_even_with_short_path_enabled() {
        let path1 = TempDir::new("module_a", "test")
            .generate_shorter_path()
            .build_path();
        let path2 = TempDir::new("module_b", "test")
            .generate_shorter_path()
            .build_path();

        assert_ne!(path1, path2);
    }

    #[test]
    fn creating_temp_dir_remove_existing_content() {
        let builder = TempDir::new("temp_dir", "creating_temp_dir_remove_existing_content");
        let (existing_dir, existing_file) = {
            let path = builder.build_path();
            (path.join("existing_subdir"), path.join("existing_file.md"))
        };

        fs::create_dir_all(&existing_dir).unwrap();
        let mut file = fs::File::create(&existing_file).unwrap();
        file.write_all(b"file content").unwrap();

        builder.build();

        assert!(
            existing_file.exists().not(),
            "should have cleaned up existing files"
        );
        assert!(
            existing_dir.exists().not(),
            "should have cleaned up existing subdirectory"
        );
    }
}